The present invention relates to image detection methods, and more specifically to a bar code image enhancement system and method for vision scanners, or devices which electronically capture an image of an item containing a bar code label and decode the bar code label from the image.
Bar code labels are widely used on merchandise items to encode price and item information for efficient checkout. Bar code labels often present the highest contrast and contain the sharpest edges in images produced by vision scanners.
Bar code label decoding involves the steps of locating and decoding. The step of locating involves determining the existence of a bar code label and then determining its location and orientation. To locate a bar code label in an image, an edge detection enhancement process may be performed, based on the fact that bar code labels contain sharp edges.
A discussion of popular edge enhancement methods can be found in the books "Digital. Image Processing" by W. K. Pratt, Wiley, New York, 1978; "Digital. Image Processing" by Gonzales and Wintz,. Addison-Wesley, London, 1977; and "Techniques for. Image Processing and Classification in Remote Sensing" by R. A. Schowengertt,. Academic Press, Orlando, 1983. These books are hereby incorporated by reference.
Edge enhancement methods are typically complex. They usually employ convolutions or transforms to enhance the high frequency elements in an image. Use of convolutions necessarily involves long integer operations as well as many multiplication operations. Use of transforms involves floating point arithmetic, which is also computationally intense. Schowengertt teaches a simple method involving absolute value calculations. Although the absolute value method is simpler than other known methods, it does not produce results which are as good as the other methods.
Therefore, it would be desirable to provide a bar code edge image enhancement method which is computationally simple, but which works as well as known image processing methods.